Pack housing and battery pack comprising same

Abstract

According to exemplary embodiments, a pack housing is provided. The pack housing comprises: a bottom plate; a crossbeam on the bottom plate; and fusible fastening assemblies coupled to the bottom plate and the crossbeam, wherein each of the fusible fastening assemblies comprises a fusible nut embedded in the crossbeam and a bushing embedded in the crossbeam.

Description

Pack housing and battery pack including the same

[0001] The present invention relates to a pack housing and a battery pack comprising the same. The present application claims the benefit of Korean application No. 10-2024-0142715, filed on October 18, 2024, which is incorporated herein by reference in its entirety.

[0002] Unlike primary batteries, secondary batteries can be charged and discharged multiple times. Secondary batteries are widely used as energy sources for various wireless devices such as handsets, laptops, and cordless vacuum cleaners. Recently, as the manufacturing cost per unit capacity of secondary batteries has decreased dramatically due to improved energy density and economies of scale, and as the driving range of BEVs (battery electric vehicles) has increased to a level equivalent to that of fuel vehicles, the primary use of secondary batteries is shifting from mobile devices to mobility.

[0003] The trend in the technological development of secondary batteries for mobility is the improvement of energy density and safety. The safety of secondary batteries for mobility is critical as it is directly related to the lives of passengers. The safety of secondary batteries can be achieved through mechanical robustness, the reliability of electrical insulation, and the delay of heat transfer in the event of a thermal runaway event.

[0004] The problem that the technical concept of the present invention aims to solve is to provide a pack housing having enhanced safety and a battery pack including the same.

[0005] According to exemplary embodiments of the present invention for solving the above-described problem, a pack housing is provided. The pack housing comprises a bottom plate; a cross beam on the bottom plate; and meltable fixing assemblies coupled to the bottom plate and the cross beam, wherein each of the meltable fixing assemblies comprises a meltable nut embedded in the cross beam and a bushing embedded in the cross beam.

[0006] The above-mentioned fused nut is surrounded by the above-mentioned bushing and the above-mentioned cross beam.

[0007] The above-mentioned molten nut is secured to the cross beam by the above-mentioned bushing.

[0008] The above bushing is welded to the above cross beam.

[0009] The cross beam includes a hole, the hole includes a first part having the fused nut and a second part having the bushing, and the width of the first part and the width of the second part are different.

[0010] The width of the first part above is smaller than the width of the second part above.

[0011] The inner surface of the above bushing does not include screw threads.

[0012] The inner surface of the above bushing does not include screw threads.

[0013] The melting point of the above-mentioned fused nut is different from the melting point of the above-mentioned bushing.

[0014] The melting point of the above-mentioned fused nut is lower than the melting point of the above-mentioned bushing.

[0015] Each of the above-mentioned meltable fixing assemblies further includes a nut between the cross beam and the bottom plate.

[0016] The above nut is welded to the above bottom plate.

[0017] The above nut contacts the above bushing and is spaced apart from the above cross beam.

[0018] The width of the above nut is different from the width of the above bushing.

[0019] The width of the above nut is smaller than the width of the above bushing.

[0020] The inner surface of the above bushing is smooth.

[0021] According to exemplary embodiments of the present invention, when a thermal runaway event occurs in battery cell assemblies, the molten nuts embedded in the cross beams may melt. Accordingly, the bottom plate and the cross beams may be separated, thereby securing a space for venting between them, which may delay heat propagation and enhance the safety of the pack housing and the battery pack containing it.

[0022] The effects obtainable from the exemplary embodiments of the present invention are not limited to those mentioned above, and other unmentioned effects can be clearly derived and understood by those skilled in the art to which the exemplary embodiments of the present disclosure belong from the following description. That is, unintended effects resulting from the implementation of the exemplary embodiments of the present disclosure can also be derived by those skilled in the art from the exemplary embodiments of the present disclosure.

[0023] FIG. 1 is a plan view showing a battery pack according to exemplary embodiments.

[0024] Figure 2 is a cross-sectional view taken along the cutting line 1A-1A' of Figure 1.

[0025] Figure 3 is a cross-sectional view taken along the cutting line 1B-1B' of Figure 1.

[0026] FIG. 4 is a plan view showing a battery pack according to exemplary embodiments.

[0027] Figure 5 is a cross-sectional view taken along the cutting line 4A-4A' of Figure 4.

[0028] Figure 6 is a cross-sectional view taken along the cutting line 4B-4B' of Figure 4.

[0029] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor can appropriately define the concepts of terms to best describe his invention, they should be interpreted in a meaning and concept consistent with the technical spirit of the present invention.

[0030] Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention; thus, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0031] In addition, in describing the present invention, if it is determined that a detailed description of related known components or functions may obscure the essence of the invention, such detailed description is omitted.

[0032] Since embodiments of the present invention are provided to more fully explain the invention to those skilled in the art, the shapes and sizes of the components in the drawings may be exaggerated, omitted, or schematically depicted for clearer explanation. Accordingly, the size or proportion of each component does not entirely reflect the actual size or proportion.

[0033]

[0034] (1st and 2nd embodiments)

[0035] FIG. 1 is a plan view showing a battery pack (100) according to exemplary embodiments.

[0036] Figure 2 is a cross-sectional view taken along the cutting line 1A-1A' of Figure 1.

[0037] Figure 3 is a cross-sectional view taken along the cutting line 1B-1B' of Figure 1.

[0038] Referring to FIGS. 1 to 3, the battery pack (100) may include a pack housing (110), a plurality of battery cell assemblies (120), and support structures (130). The battery pack (100) may be a final product mounted in an application such as a vehicle.

[0039] The pack housing (110) may provide a space for mounting a plurality of battery cell assemblies (120). The pack housing (110) may include a bottom plate (111), side walls (112), a center beam (113), cross beams (114), and a plurality of meltable fixing assemblies (MFA).

[0040] Here, two directions substantially parallel to the mounting surface (111M) of the base plate (111) are defined as the X direction and the Y direction, and a direction substantially perpendicular to the mounting surface (111M) of the base plate (111) is defined as the Z direction. The X direction, the Y direction, and the Z direction may be substantially perpendicular to each other. The mounting surface (111M) may face a plurality of battery cell assemblies (120). The base plate (111) may have a flat plate shape. The base plate (111) may include metal.

[0041] Side walls (112) may be located at the edges of the bottom plate (111). Side walls (112) may be attached to the bottom plate (111). Side walls (112) may be fixed to the bottom plate (111) by methods such as bolting and welding. Side walls (112) may horizontally surround a plurality of battery cell assemblies (120). Side walls (112) may comprise metal.

[0042] The center beam (113) may extend in the X direction. The center beam (113) may be surrounded by side walls (112). The center beam (113) may be joined to the bottom plate (111). The center beam (113) may be fixed to the bottom plate (111) by either welding or bolting. The center beam (113) may comprise metal.

[0043] Each of the cross beams (114) may extend in the Y direction. The cross beams (114) may be surrounded by side walls (112). The cross beams (114) may be joined to the bottom plate (111). A center beam (113) may be located between the cross beams (114). Each of the cross beams (114) may contain metal.

[0044] Each of the cross beams (114) may include a plurality of holes (114H). Each of the plurality of holes (114H) may include a first part (114H1) and a second part (114H2). The first part (114H1) may be spaced further away from the bottom plate (111) than the second part (114H2). The width of the first part (114H1) may differ from the width of the second part (114H2). The width of the first part (114H1) may be smaller than the width of the second part (114H2). Each of the cross beams (114) may have a solid structure. A plurality of holes (114H) may be formed by processing the cross beams (114) with mechanical tooling.

[0045] Each of the plurality of holes (114H) may extend from the lower surface of the cross beams (114). The lower surface of the cross beams (114) may face the mounting surface (111M). Each of the plurality of holes (114H) may face the mounting surface (111M).

[0046] In the following, the width of an element may be the width of the element in a direction parallel to the mounting surface (111M) of the base plate (111). For example, the width may be one of the length in the X direction, the length in the Y direction, and the length in a direction parallel to the mounting surface (111M) and oblique to the X direction and the Y direction, respectively.

[0047] The cross beams (114) can be fixed to the base plate (111) by a plurality of molten fixing assemblies (MFA). Each of the plurality of molten fixing assemblies (MFA) may include a molten nut (115), a bushing (116), and a bolt (117).

[0048] A melting nut (115) may be in the first hole (114H1). The melting nut (115) may be embedded in a corresponding cross beam (114). The inner surface of the melting nut (115) may face a bolt (117). The inner surface of the melting nut (115) may include threads for fastening with the bolt (117).

[0049] The melting nut (115) may contain a material that melts at high temperatures, such as plastic, for example. The melting point of the melting nut (115) may differ from the melting point of each of the cross beams (114). The melting point of the melting nut (115) may be lower than the melting point of each of the cross beams (114). The melting point of the melting nut (115) may differ from the melting point of the bushing (116). The melting point of the melting nut (115) may be lower than the melting point of the bushing (116). The melting point of the melting nut (115) may differ from the melting point of the bolt (117). The melting point of the melting nut (115) may be lower than the melting point of the bolt (117).

[0050] In the event that a thermal runway occurs in an adjacent of the plurality of battery cell assemblies (120), the molten nut (115) may melt. Here, thermal runway is an uncontrollable positive feedback condition in which a temperature change in the plurality of battery cell assemblies (120) further accelerates the temperature change. The plurality of battery cell assemblies (120) in a thermal runway state exhibit a rapid temperature rise and emit a large amount of high-pressure gas and combustion residue. According to exemplary embodiments, in the event of a thermal runway, the melting of the molten nut (115) causes the bottom plate (111) and the cross beams (114) to separate and promotes venting through the space between the bottom plate (111) and the cross beams (114), thereby delaying or preventing heat propagation and thereby enhancing the safety of the battery pack (100).

[0051] The bushing (116) may be embedded in a corresponding cross beam (114). The bushing (116) may be in a second hole (114H2). The bushing (116) may be fixed to a corresponding cross beam (114). The bushing (116) may be welded to a corresponding cross beam (114). A fused nut (115) may be fixed to a corresponding cross beam (114) by the bushing (116). The fused nut (115) may be surrounded by a corresponding cross beam (114) and the bushing (116). The bushing (116) may not include threads. The inner surface of the bushing (116) may be smooth. The bushing (116) may include metal.

[0052] The bolt (117) can penetrate the bottom plate (111). The bottom plate (111) may include a plurality of holes (111H). Each bolt (117) of the plurality of molten fixing assemblies (MFA) can pass through a corresponding one of the plurality of holes (111H). The bolt (117) may include metal.

[0053] The bolt (117) can be fastened to the molten nut (115). The bolt (117) may include threads for fastening to the molten nut (115). The bolt (117) may include a flange (117F) and a cylindrical portion (117S). The flange (117F) of the bolt (117) may have a wider width than the cylindrical portion (117S) of the bolt (117). The cylindrical portion (117S) of the bolt (117) may include a portion facing the bottom plate (111), a portion facing the bushing (116), and a portion facing the molten nut (115). The portion of the cylindrical portion (117S) of the bolt (117) facing the bottom plate (111) may have a smooth surface. The portion of the cylindrical part (117S) of the bolt (117) facing the bottom plate (111) may not include threads. The portion of the cylindrical part (117S) of the bolt (117) facing the bushing (116) may have a smooth surface. The portion of the cylindrical part (117S) of the bolt (117) facing the bushing (116) may not include threads. The portion of the cylindrical part (117S) of the bolt (117) facing the fused nut (115) may include threads.

[0054] The flange (115F) may be in contact with the bottom surface (111B) of the base plate (111). The bottom surface (111B) of the base plate (111) may be opposite to the mounting surface (111M). The flange (115F) may be spaced apart from the mounting surface (111M).

[0055] Support structures (130) can be coupled to cross beams (114). Support structures (130) can be fixed to cross beams (114). Multiple battery cell assemblies (120) can be supported by support structures (130).

[0056] The support structures (130) may include a mounting portion (131) that overlaps in the Z direction with a corresponding cross beam (114), a support portion (133) that overlaps in the Z direction with a corresponding battery cell assembly (120), and a connecting portion (135) that connects the mounting portion (131) and the support portion (133). The connecting portion (135) may be substantially perpendicular to the X direction.

[0057] The mounting portion (131) can be joined to the cross beams (114). The mounting portion (131) can be fixed to the cross beams (114) by either welding or bolting. The mounting portion (131) can be substantially perpendicular to the Z direction.

[0058] The support portion (133) may be closer to the bottom plate (111) than the mounting portion (131). The support portion (133) may support a corresponding one of the plurality of battery cell assemblies (120). The support portion (133) may include a plurality of venting holes (130H) that expose the lower portion of a corresponding one of the plurality of battery cell assemblies (120). The support portion (133) may be substantially perpendicular to the Z direction. The support portion (133) may be spaced apart from the bottom plate (111). The support portion (133) may be interposed between the bottom plate (111) and a corresponding one of the plurality of battery cell assemblies (120).

[0059] The center beam (113) and cross beams (114) can isolate multiple battery cell assemblies (120) from each other. The multiple battery cell assemblies (120) can be spaced apart in the Y direction with the center beam (113) in between. The center beam (113) can be interposed between the multiple battery cell assemblies (120). The multiple battery cell assemblies (120) can be spaced apart in the X direction with the cross beams (114) in between. The cross beams (114) can be interposed between the multiple battery cell assemblies (120).

[0060] In FIG. 1, the arrangement of multiple battery cell assemblies (120) can be described as a 3 * 2 arrangement. The arrangement of multiple battery cell assemblies (120) disclosed in FIG. 1 is a non-limiting example and does not limit the technical concept of the present invention in any sense. A person skilled in the art will be able to easily arrive at a plurality of battery cell assemblies (120) arranged in an M * N arrangement (where M and N are each integers greater than or equal to 2) based on what is described herein.

[0061] A plurality of battery cell assemblies (120) may be mounted on support structures (130). A plurality of battery cell assemblies (120) may be spaced apart from the bottom plate (111). Accordingly, a space for venting may be provided between the bottom plate (111) and the support structures (130). Each of the plurality of battery cell assemblies (120) may include a plurality of battery cells, a plurality of pads, and first and second integrated circuit assemblies.

[0062] Each of the plurality of battery cells may include an electrode assembly, an electrolyte, and a case. Each of the plurality of battery cells may be any one of a cylindrical battery cell, a prismatic battery cell, and a pouch-type battery cell. The electrode assembly of the cylindrical battery cell is embedded in a cylindrical metal can. The electrode assembly of the prismatic battery cell is embedded in a prismatic metal can. The electrode assembly of the pouch-type battery cell is embedded in a pouch case comprising an aluminum laminate sheet.

[0063] An electrode assembly includes an anode, a cathode, and a separator interposed between the anode and the cathode. A jelly roll type electrode assembly includes a wound structure of an anode, a cathode, and a separator interposed between them. A stack type electrode assembly includes a plurality of sequentially stacked anodes, a plurality of cathodes, and a plurality of separators interposed between them.

[0064] According to exemplary embodiments, a plurality of battery cells may form a plurality of banks. A plurality of banks may include one or more parallel-connected battery cells. A plurality of banks may be connected in series with each other. The number of battery cells included in each of the plurality of banks and the number of banks connected in series with each other may be determined according to the voltage and current to be output through each of the plurality of battery cell assemblies (120).

[0065] According to exemplary embodiments, a plurality of pads may comprise a compressible material. A plurality of pads may be interposed between a plurality of battery cells. A plurality of pads may absorb swelling of a plurality of battery cells. According to exemplary embodiments, a plurality of pads may be a thermal barrier.

[0066] The first integrated circuit assembly may include an insulating frame, an integrated circuit, busbars, wiring, and an insulating cover. The integrated circuit assembly may include physical and functional configurations for providing electrical connections between a plurality of battery cells, outputting the resulting voltage of the plurality of battery cells, and measuring the voltage (or current) of nodes within a circuit composed of the plurality of battery cells.

[0067] The insulating frame may include an insulating material such as plastic. The insulating frame may cover the front of multiple battery cells. The insulating frame may support integrated circuits, bus bars, and wiring.

[0068] The bus bars can be short-circuited to the positive leads of the battery cells of the first bank and the negative leads of one or more battery cells of the last bank. The bus bars can be welded to the positive leads of the battery cells of the first bank and the negative leads of one or more battery cells of the last bank. The resulting voltage of each of the plurality of battery cells of the plurality of battery cell assemblies (120) can be output through the bus bars. The bus bars can be fixed to an insulating frame.

[0069] The integrated circuit can be mounted on an insulating frame. Positive leads and negative leads welded to each other can form nodes within each of the plurality of battery cell assemblies (120). The integrated circuit can be configured to measure the voltage of the nodes through sensing plates and sensing bars.

[0070] The sensing bars may include a conductive material. The sensing bars may have a rod shape. The sensing bars may be short-circuited to the bus bars. The sensing bars may be coupled to the bus bars. Through the sensing bars, the voltage of the bus bars can be measured.

[0071] Each of the plurality of sensing plates may have a patch shape or a pad shape. The plurality of sensing plates may include a conductive material. The plurality of sensing plates may be short-circuited to corresponding positive leads and negative leads of the plurality of battery cells.

[0072] Each of the multiple sensing plates can be connected to an integrated circuit. Through the multiple sensing plates, the voltage of multiple nodes within the multiple battery cell assemblies (120) can be measured.

[0073] The insulating cover may include an insulating material such as plastic. The insulating cover may be fitted into an insulating frame. The insulating cover may cover integrated circuits and bus bars, and accordingly, the electrical elements of the first and second integrated circuit assemblies may be protected.

[0074] The second integrated circuit assembly may include an insulating frame, an integrated circuit, busbars, wiring, and an insulating cover. The second integrated circuit assembly is substantially identical to the first integrated circuit assembly except that it does not include busbars.

[0075] The battery pack (100) may further include leads coupled to the side walls (112) of the pack housing (110). The leads may cover elements mounted inside the battery pack (100), such as a plurality of battery cell assemblies (120) and electrical components. The leads may be secured to the pack housing (110) by mechanical coupling means, such as bolting.

[0076] The battery pack may further include exhaust devices coupled to the pack housing (110) or the lead. The pack housing (110) or the lead may include exhaust holes connected to the exhaust devices. In the event that a thermal runaway event occurs in a plurality of battery cell assemblies (120), the exhaust devices may be configured to delay thermal propagation by releasing high-temperature gas inside the battery pack (100) to the outside.

[0077] The battery pack (100) may further include a Battery Management System (BMS). The BMS may be configured to perform monitoring, balancing, and control of the battery pack (100). Monitoring of the battery pack (100) may include measuring the voltage and current of specific nodes within a plurality of battery cell assemblies (120) and measuring the temperature of set locations within the battery pack (100). The battery pack (100) may include measuring instruments for measuring the voltage, current, and temperature described above.

[0078] Balancing of the battery pack (100) is an operation that reduces deviations between multiple battery cell assemblies (120). Control of the battery pack (100) includes preventing overcharging, over-discharging, and overcurrent. Through monitoring, balancing, and control, the battery pack (100) can operate under optimal conditions, and accordingly, the shortening of the lifespan of each of the multiple battery cell assemblies (120) can be prevented.

[0079] The battery pack (100) may further include additional electrical components such as a cooling device, a Power Relay Assembly (PRA), and a safety plug. The cooling device may include a cooling fan. The cooling fan can prevent overheating of each of the multiple battery cell assemblies (120) by circulating air inside the battery pack (100). The PRA may be configured to supply or cut off power from the high-voltage battery to an external load (e.g., a vehicle motor). The PRA can protect the multiple battery cell assemblies (120) and the external load (e.g., a vehicle motor) by cutting off power supply to the external load (e.g., a vehicle motor) in situations where abnormal voltage occurs, such as a voltage surge.

[0080] The battery pack (100) may further include a plurality of interbusbars configured to electrically connect a plurality of battery cell assemblies (120). The plurality of battery cell assemblies (120) may be connected in series by the plurality of interbusbars. Accordingly, the battery pack (100) may be configured to output a high voltage to an external load (e.g., a motor of a vehicle).

[0081]

[0082] (3rd and 4th embodiments)

[0083] FIG. 4 is a plan view showing a battery pack (100') according to exemplary embodiments.

[0084] Figure 5 is a cross-sectional view taken along the cutting line 4A-4A' of Figure 1.

[0085] Figure 6 is a cross-sectional view taken along the cutting line 4B-4B' of Figure 1.

[0086] Referring to FIGS. 4 through 6, a battery pack (100') may include a pack housing (110'), a plurality of battery cell assemblies (120), and support structures (130). The battery pack (100') may be a final product mounted in an application such as a vehicle. Since the battery cell assemblies (120) and support structures (130) are substantially the same as those described with reference to FIGS. 1 through 3, a redundant description thereof is omitted.

[0087] The pack housing (110') may provide a space for mounting a plurality of battery cell assemblies (120). The pack housing (110) may include a bottom plate (111), side walls (112), a center beam (113), cross beams (114), and a plurality of meltable fixing assemblies (MFA'). Since the bottom plate (111), side walls (112), center beam (113), and cross beams (114) are substantially the same as those described with reference to FIGS. 1 through 3, a redundant description thereof is omitted.

[0088] The cross beams (114) can be fixed to the base plate (111) by a plurality of molten fixing assemblies (MFA'). Each of the plurality of molten fixing assemblies (MFA) may include a molten nut (115), a bushing (116), a bolt (117), and a nut (118). Since the molten nut (115), bushing (116), and bolt (117) are substantially the same as those described with reference to FIGS. 1 through 3, a redundant description thereof is omitted.

[0089] The nut (118) may be located between the corresponding base plate (111) and the cross beams (114). Each of the cross beams (114) may be spaced apart from the base plate (111). The nut (118) may be welded to the base plate (111). Liquid sealing may be provided for a plurality of holes (111H) of the base plate (111) by the nut (118). The inner surface of the nut (118) may include threads for fastening with the bolt (117). The portion of the cylindrical part (117S) of the bolt (117) facing the nut (118) may include threads. The nut (118) may be made of metal.

[0090] The nut (118) may be in contact with the bushing (116). The nut (118) may be spaced apart from each of the cross beams (114). The width of the nut (118) may differ from the width of the bushing (116). The width of the nut (118) may be smaller than the width of the bushing (116).

[0091] The melting point of the fused nut (115) may be different from the melting point of the nut (118). The melting point of the fused nut (115) may be lower than the melting point of the nut (118).

[0092]

[0093] The present invention has been described in more detail above through drawings and embodiments. However, the configurations described in the drawings or embodiments described in this specification are merely one embodiment of the present invention and do not represent all technical concepts of the present invention; therefore, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application.

Claims

1. Base plate; Cross beam on the floor plate above; and It includes a meltable fixing assembly coupled to the above-mentioned bottom plate and cross beam, and A pack housing characterized in that each of the above-described meltable fixing assemblies comprises a meltable nut embedded in the cross beam and a bushing embedded in the cross beam.

2. In Paragraph 1, Pack housing characterized in that the above-mentioned molten nut is surrounded by the above-mentioned bushing and the above-mentioned cross beam.

3. In Paragraph 1, A pack housing characterized in that the above-mentioned molten nut is fixed to the cross beam by the above-mentioned bushing.

4. In Paragraph 1, Pack housing characterized in that the bushing is welded to the cross beam.

5. In Paragraph 1, The above cross beam includes a hole, The above hole includes a first part having the above-mentioned molten nut and a second part having the above-mentioned bushing, and A pack housing characterized in that the width of the first part and the width of the second part are different.

6. In Paragraph 5, A pack housing characterized in that the width of the first part is smaller than the width of the second part.

7. In Paragraph 1, A pack housing characterized in that the inner surface of the bushing does not include screw threads.

8. In Paragraph 1, A pack housing characterized in that the inner surface of the bushing does not include screw threads.

9. In Paragraph 1, A pack housing characterized in that the melting point of the above-mentioned fused nut is different from the melting point of the above-mentioned bushing.

10. In Paragraph 1, A pack housing characterized in that the melting point of the above-mentioned fused nut is lower than the melting point of the above-mentioned bushing.

11. In Paragraph 1, A pack housing characterized in that each of the above-described meltable fixing assemblies further includes a nut between the cross beam and the bottom plate.

12. In Paragraph 11, Pack housing characterized by the above nut being welded to the above bottom plate.

13. In Paragraph 11, A pack housing characterized in that the nut is in contact with the bushing and is spaced apart from the cross beam.

14. In Paragraph 11, Pack housing characterized in that the width of the nut is different from the width of the bushing.

15. In Paragraph 11, Pack housing characterized in that the width of the nut is smaller than the width of the bushing.

16. In Paragraph 11, A pack housing characterized by the inner surface of the bushing being smooth.

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